The technical field generally relates to circuits including ground fault circuit interrupters (GFCIs). Various applications, such as submersible well pumps and the like, require that a motor be operated in or near water. However, the use of art electric device in or near water, or any other conductive fluid, can create a shock hazard. Typical circuit breakers do not provide adequate protection from shock hazards.
GFCI circuit breakers provide adequate protection from shock hazards but have many drawbacks. A GFCI detects a difference in current, typically at an outlet or other line in, and interrupts the circuit if a variation between conductors of approximately 5 milliamps is detected. The current difference which will trigger a GFCI fault can be very small relative to a current difference which will trip a circuit breaker. Furthermore, a GFCI can often interrupt the circuit in less than one fortieth of a second. However, GFCIs are not suitable for many applications. Induction motors, for example, can cause nuisance tripping due to current leakage during motor startup. This nuisance tripping is especially prevalent with three phase motors. Once a GFCI is tripped, motor operation is prevented until the GFCI is reset. In the case of a well pump this nuisance tripping can cause great inconvenience; however, in the case of a sump pump this can cause catastrophic results such as flooding. Many applications involving induction motors presently do not require the use of a GFCI. However, in these applications there is still a risk of shock hazard. Therefore, further technological developments are desirable in this area.